The invention relates to a method and a device for monitoring the determination of a rotor angle of a rotating shaft by use of a resolver, and to a system.
In the case of machines which are moved by use of electrical drives, a so-called resolver is frequently used to determine machine movements, in that the resolver detects a rotor angle or a rotor angle change of a rotating shaft which is coupled to an electric motor, by which it is possible to determine a position of a machine element which is moved by use of the electrical drive and the shaft.
Resolvers are low-cost, magnetically operated transmitters. They use the angle-dependent coupling between at least one rotor winding and at least two stator windings. A resolver typically includes a first stator winding, a second stator winding whose winding axis is at right angles to the winding axis of the first stator winding, and a rotor winding which is connected to the rotating shaft such that they rotate together. The two stator windings are normally arranged fixed in a housing of a transmitter. The resolvers produce the rotor angle directly within a doubled pole pitch. The rotation speed can be determined from the angle change. In addition, reference is also made to the relevant specialist literature.
In safety-critical applications, a diagnostic capability is required for the transmitter system that is used. In order to allow a low-cost resolver to be used as a transmitter for safety-critical applications, it is therefore necessary for a plausibility check and monitoring of the resolver function to be carried out in addition to determination of the rotor angle by use of the resolver in order, for example, to allow malfunctions and defects in the resolver to be identified, and to cause the electrical drive to be switched off in this situation.
The invention is based on the object of providing a method and a device for monitoring the determination of a rotor angle of a rotating shaft by use of the resolver, as well as a system, which will allow reliable monitoring, which can be implemented at low cost, and which in particular can easily be integrated in conventional systems for angle determination using a resolver.
The invention achieves this object by a method, device and system for monitoring the determination of a rotor angle of a rotating shaft via a resolver, wherein the resolver comprises: a first stator winding; at least one second stator winding, whose winding axis is rotated through a predetermined angle with respect to the winding axis of the first stator winding, and at least one rotor winding, which is connected to the rotating shaft such that they rotate together, wherein for determination of the rotor angle: a first exciter AC voltage at an exciter frequency and with a first amplitude is applied to the first stator winding; a second exciter AC voltage at the exciter frequency and with a second amplitude is applied to the at least one second stator winding; and the first amplitude and the second amplitude are produced via a regulator such that no voltage is induced in the at least one rotor winding as a result of the first and the second exciter AC voltages in a stationary state, wherein a manipulated variable of the regulator maps the rotor angle, wherein the method for monitoring the determination of the rotor angle comprises the steps of: applying a first test AC voltage at a test frequency which is not the same as the exciter frequency to the first stator winding, and applying a second test AC voltage at the test frequency to the at least one second stator winding, wherein the first and the second test AC voltages are produced such that an AC voltage is induced all the time in the at least one rotor winding as a result of the first and the second test AC voltages.
In the method for monitoring the determination of a rotor angle of a rotating shaft by use of a resolver, the resolver includes a first stator winding, at least one second stator winding, whose winding axis is rotated through a predetermined angle, in particular through 90°, with respect to the winding axis of the first stator winding, and at least one rotor winding, which is connected to the rotating shaft such that they rotate together. The following steps are carried out for determination of the rotor angle: a first, in particular sinusoidal, exciter AC voltage at an exciter frequency and with a first rotor-angle-dependent amplitude is applied to the first stator winding, a second, in particular sinusoidal, exciter AC voltage at the exciter frequency and with a second rotor-angle-dependent amplitude is applied to the at least one second stator winding, and the first amplitude and the second amplitude are produced by way of a regulator such that no voltage is induced in the at least one rotor winding as a result of the first and the second exciter AC voltages in a stationary state, wherein a manipulated variable of the regulator maps the rotor angle. The magnetic alternating field which is produced as a result of the exciter signals is at right angles to an axis of the rotor winding in the stationary state. A method such as this is described in laid-open specification DE 38 34 384 A1, which to this extent is included by reference in the subject matter of the description, in order to avoid unnecessary repetitions. The following steps are carried out for monitoring the determination of the rotor angle: a first, in particular sinusoidal, test AC voltage at a test frequency which is not the same as the exciter frequency is applied to the first stator winding, and a second, in particular sinusoidal, test AC voltage at the test frequency is applied to the at least one second stator winding, wherein the first and the second test AC voltages and their amplitudes are produced as a function of the rotor angle, that is to say as a function of the manipulated variable of the regulator which maps the rotor angle, such that an AC voltage is induced all the time in the at least one rotor winding as a result of the first and the second test AC voltages. It is self-evident that the exciter AC voltages and/or the test AC voltages can also be replaced by corresponding exciter alternating currents and test alternating currents, respectively. The AC voltage which is induced in the at least one rotor winding as a result of the first and the second test AC voltages can be used for plausibility checking/monitoring of the resolver function.
In one development, the first and the second test AC voltages, in particular their amplitudes, are produced as a function of the rotor angle such that a magnetic alternating field which is produced as a result of the first and the second test AC voltages runs essentially parallel to the winding axis of the rotor winding.
In one development, the test frequency can be represented as ft=k*fe, where ft denotes the test frequency, fe denotes the exciter frequency and k is a rational number greater than zero. Preferably, k=2, that is to say the test frequency is twice as great as the exciter frequency.
In one development, only those signal components which are induced in the rotor winding and are produced by the first and the second exciter AC voltages are used for determination of the rotor angle, that is to say the contributions of the test AC voltages are suppressed for rotor angle determination.
In one development, signal components which are induced in the rotor winding as a result of the first and the second test AC voltages are evaluated in order to determine a line break, a short circuit and/or a mechanical defect in the resolver, and/or are evaluated for redundant determination of the rotor angle.
In one development, a voltage which is induced in the at least one rotor winding as a result of the exciter AC voltages and the test AC voltages is separated via correlation into signal components which are induced in the rotor winding as a result of the test AC voltages and into signal components which are induced in the rotor winding as a result of the exciter AC voltages. This allows an evaluation to be carried out separately on the basis of signal components, that is to say the rotor angle can be determined in the conventional manner on the basis of only those signal components which are induced in the rotor winding exclusively as a result of the exciter AC voltages, without any need for complex filters for this purpose, in order to suppress those signal components, which to this extent are disturbing and are caused by the test AC voltages.
The device for monitoring the determination of a rotor angle of a rotating shaft is designed to carry out the method mentioned above and includes: a module for application of a first, in particular sinusoidal, exciter AC voltage at an exciter frequency and with a first rotor-angle-dependent amplitude to the first stator winding, a module for application of a second, in particular sinusoidal, exciter AC voltage at the exciter frequency and with a second rotor-angle-dependent amplitude to the at least one second stator winding, and a module for production of the first amplitude and of the second amplitude by way of a regulator such that no voltage is induced in the at least one rotor winding as a result of the first and the second exciter AC voltages in a stationary state, wherein a manipulated variable of the regulator maps the rotor angle. The following are also provided: a module for application of a first, in particular sinusoidal, test AC voltage at a test frequency which is not the same as the exciter frequency, to the first stator winding, a module for application of a second, in particular sinusoidal, test AC voltage at the test frequency to the at least one second stator winding, wherein the first and the second test AC voltages and their amplitudes are produced as a function of the rotor angle such that an AC voltage is induced all the time in the at least one rotor winding as a result of the first and the second test AC voltages, and also a module for evaluation of signal components which are induced in the rotor winding as a result of the first and the second test AC voltages, in order to determine a line break, a short circuit and/or a mechanical defect in the resolver, and/or for redundant determination of the rotor angle.
The system includes a resolver and a resolver monitoring device as mentioned above.